The present invention relates to a magnetic bubble memory apparatus. More particularly, it relates to the construction of a module including a magnetic bubble memory device and its analog peripheral circuits, which are easily mountable on a printed circuit board of a storage apparatus.
A semiconductor memory device such as an integrated circuit (IC) memory device plays a major role as a storage apparatus of large capacity used for an electronic apparatus such as a computer. However, because of the volatility of the storage, an auxiliary storage is indispensable so that the data can be sheltered and maintained before operation is resumed after a power down. On the contrary, a magnetic bubble memory device is a non-volatile memory device that is capable of storing data information without a power supply. In addition, the magnetic bubble memory device has many advantages such as an easy rewriting function, high reliability due to having no moving elements, compact size, a structure that is suitable for mounting onto a printed circuit board, etc. As such, the field of application of magnetic bubble memory devices has been increasing. Particularly, the magnetic bubble memory device is applicable to file memories and program loaders for various apparatuses, such as numerical control (NC) devices, robots, production control terminals, point-of-sales (POS) terminals, office automation (OA) apparatus, and the like. The constitution and operation of the magnetic bubble memory apparatuses are wellknown, but will be described briefly hereinafter to clarify the advantages of the present invention over those of the prior art.
A magnetic bubble memory device comprises substrate consisting of a magnetic garnet single crystal film epitaxially grown on a non-magnetic garnet substrate (a gadolinimium-galliumgarnet, GGG, substrate), and a transfer circuit, generator circuit and detector circuit as well as means for retaining and transferring the magnetic bubbles which are formed on the single crystal film.
Generally, a magnetic bubble memory device has a structure as shown in the perspective view of FIG. 1, comprising a memory chip 102 mounted on an insulator substate 101, an X-Y coil 103, permanent magnet plates referred as bias magnets 104, ferrite yokes 105, lead terminals 106, and a shield case 107. The X-Y coil 103 generates a rotating magnetic field which is applied to the memory chip 102 to transfer magnetic bubbles stored in the chip 102. The bias magnets 104 and the ferrite yokes 105 apply a bias magnetic field to the memory chip 102 in order to retain the magnetic bubbles therein. The lead terminals 106 connect the magnetic bubble chip 102 to associated peripheral circuits for controlling the bubble movement and for feeding out the output signals. The entire device is accommodated in a shield case 107.
FIG. 2 illustrates a schematic plan view of a pattern configuration formed on a magnetic bubble memory chip 102. On a magnetic garnet crystal film grown epitaxially on a non-magnetic garnet substrate (not shown), various elements are formed: a bubble generator 111 coupled with a write-in major line 112, a large number of minor loops 113 for storing information and a read-out major line 114, wherein both the write-in and read-out major lines 112, 114 couple with the minor loops 113. The major lines 112 and 114, and the minor loops 113, are composed of a series of conductor patterns, such as half disk-shaped patterns, as an example. The conductor patterns are formed of iron-nickel alloy (Permalloy) having a high magnetic permeability by a conventional film forming method, and the magnetic bubbles are transferred therethrough and stored therein. A group of signals stored in the patterns located on a horizontal line (shown in FIG. 2 by the dotted line A--A) is referred as a page.
When write-in signals are input to the bubble generator 111, bubble signals are generated therein and, under the control of swap-gate 115, bubble signals are transferred in sequence so as to compose a page, which is transferred through the major line 112 to a minor loop 113 by driving the X-Y coil 103.
When read-out signals are input, the stored information signals in the form of magnetic bubbles are copied by a replicate gate 116 and transferred to a detector 117 which is made of Permalloy. Accordingly, the information signals are converted to current signals by utilizing the magnetoresistance effect of Permalloy, namely by detecting the difference of resistance of respective Permalloy patterns. The current signals are amplified and converted to a TTL (transistor-transistor logic) level by a sense amplifier (not shown). A boot loop 119, a boot swap gate 120 and a boot replicate gate 121 provide information with regards to inherent defects of the minor loops 113 to skip these defects during write-in and read-out operations.
These gates are driven by respective analog drivers, the analog circuits of which require analog technology for their design. These analog circuits comprise function drivers, a coil driver and a sense amplifier. These circuits are referred to as analog peripheral circuits. On the other hand, a magnetic bubble memory apparatus has a group of digital circuits that are referred to as digital peripheral circuits and which provide digital signals to control the analog circuits according to write-in signals or read-out signals provided by an exterior controlling circuit.
As described above, a magnetic bubble memory apparatus comprises magnetic bubble memory devices, analog peripheral circuits and digital peripheral circuits, which are usually mounted on a printed circuit board. As a result, the magnetic bubble memory apparatus is to be built into a user's apparatus as its storage unit, utilizing electrical connecting means such as connectors and mechanical fixing means such as fixing frames. It is desirable to mount a magnetic bubble memory apparatus in a module type container onto a printed circuit board without such connectors and fixing frames. Recently, users tend to demand a magnetic bubble memory device which can be handled for mounting on a printed circuit board in the same manner as other electronic elements, to obtain freedom of design and ease of mounting.